add util.inspect data to 'type not printable'. Add test to cover these lines (no existing test).

packages/node_modules/@node-red/util/lib/util.js

@@ -755,7 +755,7 @@ function encodeObject(msg,opts) {
                     }," ");
                 } else {
                     try { msg.msg = msg.msg.toString(); }
-                    catch(e) { msg.msg = "[Type not printable]"; }
+                    catch(e) { msg.msg = "[Type not printable]" + util.inspect(msg.msg); }
                 }
             }
         } else if (msgType === "function") {

test/unit/@node-red/util/lib/util_spec.js

@@ -822,6 +822,53 @@ describe("@node-red/util/util", function() {
                 success.should.eql(1);
                 done();
             });
+            it('very large object which fails to serialise should be truncated', function(done) {
+                var msg = {
+                    msg: {
+                        obj:{
+                            big:"",
+                            cantserialise:{
+                                message:'this will not be displayed',
+                                toJSON: function(val) {
+                                    throw new Error('this exception should have been caught');
+                                    return 'should not display because we threw first';
+                                },
+                            },
+                            canserialise:{
+                                message:'this should be displayed',
+                            }
+                        },
+                    }
+                };
+                
+                for (var i = 0; i < 1000; i++) {
+                  msg.msg.obj.big += 'some more string ';
+                }
+                
+                var result = util.encodeObject(msg);
+                result.format.should.eql("error");
+                var resultJson = JSON.parse(result.msg);
+                var success = (resultJson.message.length <= 1000);
+                success.should.eql(true);
+                done();
+            });
+            it('test bad toString', function(done) {
+                var msg = {
+                    msg: {
+                      mystrangeobj:"hello",
+                    },
+                };
+                msg.msg.toString = function(){
+                  throw new Error('Exception in toString - should have been caught');
+                }
+                msg.msg.constructor = { name: "strangeobj" };
+                
+                var result = util.encodeObject(msg);
+                var success = (result.msg.indexOf('[Type not printable]') >= 0);
+                success.should.eql(true);
+                done();
+            });
+
             
         });
     });